Effect of polyamidoamine (PAMAM) dendrimers on the in vitro release of water-insoluble nifedipine from aqueous gels

The objective of this study was to determine the effect of ethylenediamine core PAMAM dendrimers, on the release of nifedipine suspended in aqueous gels and to correlate release to the increase in solubility afforded by the dendrimers. Drug release from aqueous 5% HPMC gels containing nifedipine (2% wt/vol) through 0.2-μm membranes was measured using Enhancer cells and 50% ethanolic solution as the receptor medium. The release from gels containing PAMAM G-3 and G-5 (0.25%–1% wt/vol) was compared with gels containing the cosolvent isopropyl alcohol (10%–80% vol/vol). PAMAM dendrimers significantly increased the solubility of nifedipine. This caused a significant increase in the release rate of nifedipine from the gel suspensions. The increase in drug release depended on the concentration and generation size of the dendrimers added. For higher generations (G-5) lower concentrations were needed to obtain equivalent increases in release. Although the increase in solubility and release was not as high as from gels containing high concentrations of the cosolvent isopropyl alcohol, the dendrimers prevented the recrystallization of the drug that was observed when the gels containing isopropyl alcohol were left open. Published: October 24, 2005     

Factors influencing regeneration from protoplasts of Asparagus densiflorus cv. Sprengeri

This article describes conditions to optimize the yield of viable protoplasts from callus tissue of Asparagus densiflorus cv. Sprengeri and their subsequent regeneration into plantlets. Callus tissue was initiated by culturing spear sections (5–7 mm) on Murashige and Skoog (MS) medium supplemented with 0.8% (wt/vol) Bacto agar, 3% (wt/vol) sucrose, 0.5 mg/l each of nicotinic acid, pyridoxine-HCl, and thiamine-HCl, 1 mg/l p-chlorophenoxyaceticacid (pCPA) and 1 mg/l 6-benzylaminopurine (BAP). The maximum protoplast yield was obtained in a mixture of 1% (wt/vol) Cellulysin, 0.8% (wt/vol) Rhozyme HP 150 and 0.3% (wt/vol) Macerase, dissolved in cell protoplast wash salt solution with 7 mm CaCl₂ ^.2H₂O, 3 mm MES, 0.6 m glucose, and 0.1 m mannitol. First divisions were observed after 3–4 days of initial culture. The plating efficiency was highest (7.8%) in half-strength MS semisolid medium containing 1 g/l glutamine, 0.6 m glucose, 0.1 m mannitol, 0.5 mg/l folic acid, 0.05 mg/l biotin, 2 mg/l ascorbic acid, 1 mg/l α-naphthaleneacetic acid, 0.5 mg/l zeatin, and 0.1% (wt/vol) Gelrite. Protoplast-derived microcolonies and microcalli were cultured on the same medium on which the primary callus culture was initiated. After 10–12 weeks, calli were transferred to shoot regeneration medium containing MS salts, 1 mg/l BAP, 0.5 mg/l pCPA and 0.2% Gelrite. Shoots (3–4 cm) were then transferred to MS rooting medium with 2 mg/l indole-3-butyric acid, and 0.2% Gelrite. Plantlets were obtained within 4–5 weeks. Received: 9 August 1995 / Revision received: 27 June 1997 / Accepted: 17 July 1997     

Glucose Fermentation by <Emphasis Type="Italic">Propionibacterium microaerophilum</Emphasis>: Effect of pH on Metabolism and Bioenergetic

pH affected significantly the growth and the glucose fermentation pattern of Propionibacterium microaerophilum. In neutral conditions (pH 6.5–7.5), growth and glucose fermentation rate (qs) were optimum producing propionate, acetate, CO₂, and formate [which together represented 90% (wt/wt) of the end products], and lactate representing only 10% (wt/wt) of the end products. In acidic conditions, propionate, acetate, and CO₂ represented nearly 100% (wt/wt) of the fermentation end products, whereas in alkaline conditions, a shift of glucose catabolism toward formate and lactate was observed, lactate representing 50% (wt/wt) of the fermentation end products. The energy cellular yields (Y _X/ATP), calculated (i) by taking into account extra ATP synthesized through the reduction of fumarate into succinate, was 6.1–7.2 g mol⁻¹. When this extra ATP was omitted, it was 11.9–13.1 g mol⁻¹. The comparison of these values with those of Y _X/ATP in P. acidipropionici and other anaerobic bacteria suggested that P. microaerophilum could not synthesize ATP through the reduction of fumarate into succinate and therefore differed metabolically from P. acidipropionici. Received: 8 April 2002 / Accepted: 8 May 2002     

Preparation of budesonide and budesonide-PLA microparticles using supercritical fluid precipitation technology

The objective of this study was to prepare and characterize microparticles of budesonide alone and budesonide and polylactic acid (PLA) using supercritical fluid (SCF) technology. A precipitation with a compressed antisolvent (PCA) technique employing supercritical CO₂ and a nozzle with 100-μm internal diameter was used to prepare microparticles of budesonide and budesonide-PLA. The effect of various operating variables (temperature and pressure of CO₂ and flow rates of drug-polymer solution and/or CO₂) and formulation variables (0.25%, 0.5%, and 1% budesonide in methylene chloride) on the morphology and size distribution of the microparticles was determined using scanning electron microscopy. In addition, budesonide-PLA particles were characterized for their surface charge and drug-polymer interactions using a zeta meter and differential scanning calorimetry (DSC), respectively. Furthermore, in vitro budesonide release from budesonide-PLA microparticles was determined at 37°C. Using the PCA process, budesonide and budesonide-PLA microparticles with mean diameters of 1 to 2 μm were prepared. An increase in budesonide concentration (0.25%–1% wt/vol) resulted in budesonide microparticles that were fairly spherical and less aggiomerated. In addition, the size of the microparticles increased with an increase in the drug-polymer solution flow rate (1.4–4.7 mL/min) or with a decrease in the CO₂ flow rate (50–10 mL/min). Budesonide-PLA microparticles had a drug loading of 7.94%, equivalent to ∼80% encapsulation efficiency. Budesonide-PLA microparticles had a zeta potential of— 37±4 mV, and DSC studies indicated that SCF processing of budesonide-PLA microparticles resulted in the loss of budesonide crystallinity. Finally, in vitro drug release studies at 37°C indicated 50% budesonide release from the budesonide-PLA microparticles at the end of 28 days. Thus, the PCA process was successful in producing budesonide and budesonide-PLA microparticles. In addition, budesonide-PLA microparticles sustained budesonide release for 4 weeks.     

Effects of vegetation coverage on the spatial distribution of soil nematode trophic groups

The spatial variability of total soil nematodes and trophic groups in bare and fallow plots in Shenyang Experimental Station of Ecology, Chinese Academy of Sciences was examined using geostatistics combined with classic statistics. Results showed that the soil pH value had a negative effect on plant-parasites in both bare and fallow plots; the mean number of total nematodes was significantly higher in fallow plots than in bare plots, which was 1485.3 and 464.0 individuals per 100 g dry soil in fallow and bare plots, respectively; the nugget (C ₀)/sill (C ₀+C) ratio of total nematodes, plant-parasites and bacterivores were lower in fallow plots (27.3%–45.6%) than in bare plots (49.5%–100%); the spatial distribution of total nematodes and trophic groups was found to be different between fallow and bare plots, which indicated that vegetation coverage had an effect on soil nematodes. __________ Translated from Chinese Journal of Applied Ecology, 2006, 17(2): 295–299 [译自: 应用生态学报]     

Nitrogen and Phosphorus Release from Decomposing Leaves under Sub‐Humid Tropical Conditions1

For many soils of the tropics, inputs of organic materials are essential to sustain soil fertility and crop production. Research in the quality of organic inputs, a key factor controlling rates of decomposition and nutrient release, continues to guide selection and use of organic materials as nutrient sources. The relationship between decomposition patterns and the quality parameters of the fresh leaves of six agroforestry species: Sesbania sesban, Croton megalocarpus, Calliandra calothyrsus, Tithonia diversifolia, Lantana camara, and Senna spectabilis, was investigated in a litterbag study over a period of 77 days in the highlands of western Kenya. The litterbags were buried 1 cm below the soil surface and covered with soil of ca 1 cm thickness. Percent leaf mass and total N and P that remained with time strongly correlated with total P and C/P ratio (R²= 0.60‐0.90) during the first 35 days of study; but afterwards, correlation was stronger with the initial soluble polyphenolics (Pp)/P ratio (R²= 0.69‐0.92) than with total P and C/P ratio. Loss of leaf mass and release of N and P followed the exponential function, y_t= y₀* e‐^kt, from which the specific decay rate constants (k) were calculated for loss of leaf mass (k_B) and release of N (k_N) and P (K_p). Among the plant species, the k values were lowest in Calliandra with k_B= 0.012/d, k_N= 0.017/d and k_p= 0.044/d. Lantana had the highest K values with k_g= 0.067/d and k_p= 0.119/d, but the highest k_N value of 0.109/d occurred in Tithonia. The k_B values for all organic materials were lower than their corresponding k_N and k_p values, suggesting that leaching of N and P from litters may have augmented the microbial mineralization of N and P. There was a strong correlation between the k_B, k_N, and k_p values and total P (r = 0.82‐0.96; P 0.01), but not total N, lignin (LIG), or Pp. Rates of N and P release followed the general trend: Tithonia > Senna > Lantana > Sesbania > Croton > Calliandra. The results indicated that, among the quality parameters studied, total P is the most important factor controlling rate of decomposition and N and P release from organic inputs in the area of study.     

Eudragit-coated pectin microspheres of 5-fluorouracil for colon targeting

An objective of the present investigation was to prepare and evaluate Eudragit-coated pectin microspheres for colon targeting of 5-fluorouracil (FU). Pectin microspheres were prepared by emulsion dehydration method using different ratios of FU and pectin (1:3 to 1:6), stirring speeds (500–2000 rpm) and emulsifier concentrations (0.75%–1.5% wt/vol). The yield of preparation and the encapsulation efficiencies were high for all pectin microspheres. Microspheres prepared by using drug:polymer ratio 1:4, stirring speed 1000 rpm, and 1.25% wt/vol concentration of emulsifying agent were selected as an optimized formulation. Eudragit-coating of pectin microspheres was performed by oil-in-oil solvent evaporation method using coat: core ratio (5:1). Pectin microspheres and Eudragit-coated pectin microspheres were evaluated for surface morphology, particle size and size distribution, swellability, percentage drug entrapment, and in vitro drug release in simulated gastrointestinal fluids (SGF). The in vitro drug release study of optimized formulation was also performed in simulated colonic fluid in the presence of 2% rat cecal content. Organ distribution study in albino rats was performed to establish the targeting potential of optimized formulation in the colon. The release profile of FU from Eudragit-coated pectin microspheres was pH dependent. In acidic medium, the release rate was much slower; however, the drug was released quickly at pH 7.4. It is concluded from the present investigation that Eudragit-coated pectin microspheres are promising controlled release carriers for colon-targeted delivery of FU. Published: February 16, 2007     

An increased carbon dioxide production in transient hypoxia in healthy subjects at rest

Indices of pulmonary gas exchange and heart rate (HR) have been measured in 24 healthy subjects not adapted to hypoxia after hypoxic aerial mixture (HAM) (17, 15, 13 vol % of oxygen) respiration for 15 min. Using group data analysis, it has been shown that hypoxia under the conditions of inhalation of 17 and 15 vol % of O₂ caused no significant changes. Hypoxia under the conditions of 13 vol % of O₂ inhalation is a threshold one, when ventilation (SpO₂) drops below 85%. A significant increase in the lung ventilation (Ve) (10–14%, p < 0.05) and HR (11–15%, p < 0.05) have been observed in this case. Hyperpnea was accompanied by an increase in the oxygen uptake rate by 10% and carbon dioxide release rate (10–18%, p < 0.05). On the contrary, individual data analysis showed changes in the pulmonary gas exchange indices in 90% of subjects in the case of inhalation of 17 vol % of O₂ HAM. Four response types have been found: ventilation (increase in lung ventilation), hypoxic hypometabolism (decrease in oxygen consumption rate), and mobilization response (increase in oxygen utilization in the lungs), and anaerobic response, which is expressed in an increase in the carbon dioxide release rate along with an increase in the respiratory quotient. All these responses are of an individual type, but the ventilation response is developed in response to hypoxia caused by inhalation of 13 vol % of O₂ HAM and a decrease in SpO₂ below 85% in more than 60% of cases.     

Antibacterial Activities of Novel Diselenide-bridged <Emphasis Type="Italic">bis</Emphasis>(Porphyrin)s on <Emphasis Type="Italic">Staphylococcus aureus</Emphasis> Investigated by Microcalorimetry

The actions of two novel diselenide-bridged bis(porphyrin)s (1 and 2) on Staphylococcus aureus growth was investigated by microcalorimetry at 37.00°C, compared with that of Na₂SeO₃. Differences in their capacities to inhibit the growth metabolism of S. aureus were observed. By analyzing the power–time curves, crucial parameters such as the rate constant of bacterial growth (k), inhibitory rate (I), and generation time (t _G) were determined. The growth rate constant (k) of S. aureus (in the log phase) in the presence of the drugs decreased with increasing concentrations of the drugs regularly. The relationship of k and c is nearly linear for diselenide-bridged bis(porphyrin) 2. The sequence of the antibacterial activities of these selenium compounds tested was 2 > 1 > Na₂SeO₃.     

Quantitative Structure-Activity Relationships for the Pre-Steady State of <Emphasis Type="Italic">Pseudomonas Species</Emphasis> Lipase Inhibitions by <Emphasis Type="Italic">p</Emphasis>-Nirophenyl-<Emphasis Type="Italic">N</Emphasis>-Substituted Carbamates

The pre-steady states of Pseudomonas species lipase inhibitions by p-nitrophenyl-N-substituted carbamates (1–6) are composed of two steps: (1) formation of the non-covalent enzyme–inhibitor complex (E:I) from the inhibitor and the enzyme and (2) formation of the tetrahedral enzyme–inhibitor adduct (E–I) from the E:I complex. From a stopped-flow apparatus, the dissociation constant for the E:I complex, K_S, and the rate constant for formation of the tetrahedral E–I adduct from the E:I complex, k₂ are obtained from the non-linear least-squares of curve fittings of first-order rate constant (k_obs) versus inhibition concentration ([I]) plot against k_obs=k₂+k₂[I]/(K_S+[I]). Values of pK_S, and log k₂ are linearly correlated with the σ^* values with the ρ^* values of −2.0 and 0.36, respectively. Therefore, the E:I complexes are more positive charges than the inhibitors due to the ρ^* value of −2.0. The tetrahedral E–I adducts on the other hand are more negative charges than the E:I complexes due to the ρ^* value of 0.36. Formation of the E:I complex from the inhibitor and the enzyme are further divided into two steps: (1) the pre-equilibrium protonation of the inhibitor and (2) formation of the E:I complex from the protonated inhibitor and the enzyme.     

鼠李糖乳杆菌碱性磷酸酶的提取条件优化及其降解有机磷农药作用

【背景】我国作为农业大国,对农药的大量使用是不可避免的,但是农药的超范围使用、超标及高检出率对于环境的污染与人体健康的威胁日趋严重。【目的】碱性磷酸酶(alkaline phosphatase,ALP)对有机磷农药具有积极的降解作用,因此,本文对鼠李糖乳杆菌(Lactobacillus rhamnosus) Z23(LGG Z23)所产碱性磷酸酶的提取条件进行优化,并研究其对有机磷农药的降解作用。【方法】使用单因素试验和正交试验优化ALP的提取条件;使用对硝基苯酚法测定酶活力;使用分级沉淀和层析法提纯ALP;使用乙酰胆碱酯酶抑制法测定ALP对有机磷农药的降解率。【结果】LGG Z23所产ALP的最优提取条件为：细胞破碎时间15 min,破碎功率450 W,料液比(质量体积比)1:6,提取液pH 10.0,此条件下酶活力为(4.95±0.26) U/mL,比优化前提高2.11倍;对6种有机磷农药的降解率效果为敌敌畏(95.79%±0.01%)>甲基对硫磷(90.69%±0.03%)>毒死蜱(88.90%±0.02%)>敌百虫(86.07%±0.03%)>马拉硫磷(85.31%±0.02%)>乐果(83.18%±0.03%),其中对敌敌畏和甲基对硫磷的降解效果最好,可达90%以上,并且降解作用差异显著(P<0.05)。【结论】本研究为LGG Z23所产ALP的应用研究提供了理论依据和实验数据。     

Investigations on neomycin production with immobilized cells of<Emphasis Type="Italic">Streptomyces marinensis</Emphasis> Nuv-5 in calcium alginate matrix

The purpose of this investigation was to study the effect ofStreptomyces marinensis NUV-5 cells immobilized in calcium alginate for the production of neomycin. The effect of various parameters, such as the effect of alginate concentration (1%, 2%, 3%, 4%, and 5% wt/vol), the effect of cation (caCl₂, BaCl₂, and SrCl₂), the concentration of cation (0.01M, 0.125M, 0.25M, 0.375M, and 0.5M), the curing times (1, 6, 11, 16, and 21 hours), and the diameter of the bead (1.48, 2.16, 3.24, 4.46, and 5.44 mm), on neomycin production and bead stability were studied. The effect of maltose (4%, 3%, 2%, and 1% wt/vol) and sodium glutamate (0.6%, 0.3%, 0.15%, and 0.075%) wt/vol) concentration on neomycin production was also studied. Better neomycin production was achieved with optimized parameters, such as alginate at 2% wt/vol, 0.25M CaCl₂, 1-hour curing time, and 3.24 mm bead diameter. Effective neomycin production was achieved with 3% wt/vol maltose and 0.6% wt/vol sodium glutamate concentration. The repeated batch fermentations were conducted (every 96 hours) using the optimized alginate beads, employing the production medium with 3% wt/vol maltose and 0.6% wt/vol sodium glutamate along with minerals salts solution. The increase in antibiotic production was observed up to the 5th cycle, and later gradual decrease in antibiotic production was observed. Comparison of the total antibiotic production with free cells and immobilized cells was also done. An enhanced antibiotic productivity of 32% was achieved with immobilized cells over the conventional free-cell fermentation, while 108% more productivity was achieved over the washed free-cell fermentation. From these results it is concluded that the immobilized cells ofS marinensis NUV-5 in calcium alginate are more efficient for the production of neomycin with repeated batch fermentation.     

Energy Budget for the Cultured,Zooxanthellate Octocoral <Emphasis Type="Italic">Sinularia flexibilis</Emphasis>

The zooxanthellate octocoral Sinularia flexibilis is a producer of potential pharmaceutically important metabolites such as antimicrobial and cytotoxic substances. Controlled rearing of the coral, as an alternative for commercial exploitation of these compounds, requires the study of species-specific growth requirements. In this study, phototrophic vs. heterotrophic daily energy demands of S. flexibilis was investigated through light and Artemia feeding trials in the laboratory. Rate of photosynthetic oxygen by zooxanthellae in light (≈200 μmol quanta m⁻² s⁻¹) was measured for the coral colonies with and without feeding on Artemia nauplii. Respiratory oxygen was measured in the dark, again with and without Artemia nauplii. Photosynthesis–irradiance curve at light intensities of 0, 50, 100, 200, and 400 μmol quanta m⁻² s⁻¹ showed an increase in photosynthetic oxygen production up to a light intensity between 100 and 200 μmol quanta m⁻² s⁻¹. The photosynthesis to respiration ratio (P/R > 1) confirmed phototrophy of S. flexibilis. Both fed and non-fed colonies in the light showed high carbon contribution by zooxanthellae to animal (host) respiration values of 111–127%. Carbon energy equivalents allocated to the coral growth averaged 6–12% of total photosynthesis energy (mg C g ⁻ 1 buoyant weight day ⁻ 1) and about 0.02% of the total daily radiant energy. “Light utilization efficiency (ε)” estimated an average ε value of 75% 12 h ⁻ 1 for coral practical energetics. This study shows that besides a fundamental role of phototrophy vs. heterotrophy in daily energy budget of S. flexibilis, an efficient fraction of irradiance is converted to useable energy.     

Isolation of a strain of <Emphasis Type="Italic">Acidithiobacillus caldus</Emphasis> and its role in bioleaching of chalcopyrite

A moderately thermophilic and acidophilic sulfur-oxidizing bacterium named S₂, was isolated from coal heap drainage. The bacterium was motile, Gram-negative, rod-shaped, measured 0.4 to 0.6 by 1 to 2 μm, and grew optimally at 42–45°C and an initial pH of 2.5. The strain S₂ grew autotrophically by using elemental sulfur, sodium thiosulfate and potassium tetrathionate as energy sources. The strain did not use organic matter and inorganic minerals including ferrous sulfate, pyrite and chalcopyrite as energy sources. The morphological, biochemical, physiological characterization and analysis based on 16S rRNA gene sequence indicated that the strain S₂ is most closely related to Acidithiobacillus caldus (>99% similarity in gene sequence). The combination of the strain S₂ with Leptospirillum ferriphilum or Acidithiobacillus ferrooxidans in chalcopyrite bioleaching improved the copper-leaching efficiency. Scanning electron microscope (SEM) analysis revealed that the chalcopyrite surface in a mixed culture of Leptospirillum ferriphilum and Acidithiobacillus caldus was heavily etched. The energy dispersive X-ray (EDX) analysis indicated that Acidithiobacillus caldus has the potential role to enhance the recovery of copper from chalcopyrite by oxidizing the sulfur formed during the bioleaching progress.     

Genetic variation in catechol-<Emphasis Type="Italic">O</Emphasis>-methyltransferase (<Emphasis Type="Italic">COMT</Emphasis>) and obesity in the prostate,lung, colorectal,and ovarian (PLCO) cancer screening trial

Catechol-O-methyltransferase (COMT) is an important modulator in the catabolism of extraneural dopamine, which plays an important role in drug reward mechanisms. It is hypothesized that genetic variations in the COMT gene, which can result in a three to fourfold difference in COMT enzyme activity, may be associated with several reward-motivated behaviors. The aim of our study was to examine the relationship between COMT polymorphisms with smoking, obesity and alcohol. Three single nucleotide polymorphisms (SNPs) in COMT were genotyped in 2,371 participants selected randomly from the screening arm of the PLCO Cancer Screening Trial after stratifying by sex, age, and smoking status. Smoking, obesity, and alcohol consumption were assessed by questionnaire. SNP and haplotype associations were estimated using odds ratios (ORs) and 95% confidence intervals (CIs) derived from conditional logistic regression models, adjusted for race/ethnicity. The COMT Ex4-76C > G (Leu136Leu) polymorphism was statistically significantly associated with individuals who had >30% increases in BMI from ages 20 to 50 years, compared to those with 0–5% increase in BMI (0–5%) over the same age period: (CC is referent; OR_CG = 1.42, OR_GG = 1.46, P _trend = 0.06). By sex, the increased risk was further pronounced among females (OR_CG = 1.50, OR_GG = 2.10, P _trend = 0.03). Consistent with our analyses of single polymorphisms, individuals whose BMI increased >30% from ages 20 to 50 years were more likely than individuals with 0–5% increases in BMI to possess COMT haplotypes [COMT Ex3-104C > T–COMT Ex4-76 C > G–COMT Ex4-12 A > G] that included the variant allele for COMT Ex4-76 C > G: C-G-G (T-C-A is referent: OR_C-G-G = 1.33, 95% CI 1.01–1.77) and C-G-A (OR_C-G-A = 1.79, 95% CI 0.72–4.49). We observed no association between any of the COMT polymorphisms with smoking behavior or alcohol intake. The COMT Ex4-76C > G (Leu136Leu) polymorphism appears to play a role in large increases in BMI. The null association with smoking and alcohol and the pronounced association with increasing BMI among women further implicates COMT’s role in estrogen metabolism as a potentially culpable pathway. Our results support a need for comprehensive evaluation of COMT variations and their functional relevance as COMT may be an important molecular target to evaluate for new treatments regarding obesity.     

Mating system and seed variation of <Emphasis Type="Italic">Acacia</Emphasis> hybrid (<Emphasis Type="Italic">A. mangium</Emphasis> × <Emphasis Type="Italic">A. auriculiformis</Emphasis>)

The mating system and seed variation of Acacia hybrid (A. mangium × A. auriculiformis) were studied using allozymes and random amplified polymorphic DNA (RAPD) markers, respectively. Multi-locus outcrossing rate estimations indicated that the hybrid was predominantly outcrossed (mean±s.e. t _m = 0.86±0.01). Seed variation was investigated using 35 polymorphic RAPD fragments. An analysis of molecular variance (AMOVA) revealed the highest genetic variation among seeds within a pod (66%–70%), followed by among pods within inflorescence (29%–37%), and the least variation among inflorescences within tree (<1%). In addition, two to four RAPD profiles could be detected among seeds within pod. Therefore, the results suggest that a maximum of four seeds per pod could be sampled for the establishment of a mapping population for further studies.     

Study of Antibacterial Activity of ZnZnbisporphyrin Complexes and its Free Components on <Emphasis Type="Italic">Staphylococcus aureus</Emphasis> by Microcalorimetry

The antibacterial effect of Zn(II), tetraphenyl porphyrin (TPP), propdioxyl bridged tetraphenyl bisporphyrin 1, and its metallobisporphyrin complexes (ZnMnbisporphyrin 2 and ZnZnbisporphyrin 3) towards Staphylococcus aureus growth was investigated by microcalorimetry at 37°C. Differences in their capacities to inhibit the growth metabolism of S. aureus were observed. By analyzing the power–time curves, crucial parameters such as the rate constant of bacterial growth (k), inhibitory ratio (I), and generation time (t _G) were determined. The growth rate constant (k) of S. aureus (in the log phase) in the presence of the drugs decreased linearly with increasing concentrations of the complexes. The sequence of the antibacterial activities of these compounds tested was 3 > 2 > 1 > Zn(II) > TPP. ZnZnbisporphyrin 3 is proposed to benefit from the synergetic effects of Zn(II) and 1.     

Edible oil degradation by using yeast coculture of <Emphasis Type="Italic">Rhodotorula pacifica</Emphasis> ST3411 and <Emphasis Type="Italic">Cryptococcus laurentii</Emphasis> ST3412

To develop a microbial treatment of edible oil-contaminated wastewater, microorganisms capable of rapidly degrading edible oil were screened. The screening study yielded a yeast coculture comprising Rhodotorula pacifica strain ST3411 and Cryptococcus laurentii strain ST3412. The coculture was able to degrade efficiently even at low contents of nitrogen ([NH₄–N] = 240 mg/L) and phosphorus sources ([PO₄–P] = 90 mg/L). The 24-h degradation rate of 3,000 ppm mixed oils (salad oil/lard/beef tallow, 1:1 w/w) at 20°C was 39.8% ± 9.9% (means ± standard deviations of eight replicates). The highest degradation rate was observed at 20°C and pH 8. In a scaled-up experiment, the salad oil was rapidly degraded by the coculture from 671 ± 52.0 to 143 ± 96.7 ppm in 24 h, and the degradation rate was 79.4% ± 13.8% (means ± standard deviations of three replicates). In addition, a repetitive degradation was observed with the cell growth by only pH adjustment without addition of the cells.     

Type I blue copper proteins as enantioselective quenchers of the photoluminescence of Δ,Λ-Eu(pyridine-2,6-dicarboxylate)3 3–: azurin from Pseudomonas aeruginosa and its Met44→Lys mutant, amicyanin from Paracoccus versutus and parsley plastocyanin

 The dynamic quenching of the luminescence of racemic Eu(III)(pyridine-2,6-dicarboxylate=dpa)₃ ^3– by the title proteins is investigated and the enantioselectivity of the proteins in the quenching of the Δ and Λ enantiomers of Eu(dpa)₃ ^3– is determined. The two diastereomeric quenching rate constants pertaining to azurin (k _q ^Δ=3.3×10⁶, k _q ^Λ=2.7×10⁶ M^–1s^–1, pH 7.2, ionic strength I=22 mM) are lower than for its Met→44Lys mutant (k _q ^Δ=1.9×10⁷, k _q ^Λ=1.4×10⁷ M^–1 s^–1, same pH and I), indicating that energy transfer occurs from Eu(dpa)₃ ^3– to the Cu(II) centre when the luminophore is bound to the hydrophobic patch of the protein near residue 44. The enantioselectivity remains unaltered by the mutation: k _q ^Δ/k _q ^Λ=1.27±0.04, so Lys44 is probably not in direct contact with the Eu chelate. The I and pH dependence of k _q indicate that the lysine residue interacts electrostatically with Eu(dpa)₃ ^3–. For plastocyanin the quenching rates are of the order of 10⁶ M^–1 s^–1; for amicyanin they are two orders of magnitude larger (k _q ^Δ=12×10⁷, k _q ^Λ=11×10⁷ M^–1 s^–1, pH 7.2, I=22 mM). The variation of k _q is attributed to differences in the charge distribution on the proteins, which influences the binding of the luminophore to the protein surface. For amicyanin the anion binding site near Lys59 and Lys60 may be involved in the energy transfer. Received: 16 June 1998 / Accepted: 18 September 1998     

Three genetically divergent lineages of the Oryx in eastern Africa: Evidence for an ancient introgressive hybridization

Phylogeographic and population genetic studies using sequence information are frequently used to infer species boundaries and history; and to assess hybridization and population level processes. In this study, partial mitochondrial DNA (mtDNA) control region (423 bp) and cytochrome b sequences (666 bp) of Oryx beisa sampled from five isolated localities in its entire current range in Africa were analyzed to investigate the extent of genetic variation and differentiation between populations. We observed high nucleotide diversity at the control region in the total sample (6.3%) but within populations, it varied considerably ranging from 1.6% to 8.1%. Population pairwise genetic differentiation was generally significantly high (ranging from F _ST = 0.15, P<0.01 to F _ST = 0.54, P<0.001). In the total sample, 29 and 12 haplotypes were observed in the control region and the cytochrome b data sets respectively. For both data sets, the haplotypes cluster into three distinct clades (sequence divergence ranged from 6.0%–12.9% to 0.8%–1.0% for the control region and cytochrome b sequences, respectively) that do not correspond to sampling locations. Two of these clades are found in the same localities (Samburu and Marsabit), which represent the O.beisa beisa subspecies, whereas the last clade represents the fringe-eared oryx (O. beisa callotis). We interpret these findings in terms of an ancient hybridization and introgression between two formerly isolated taxa of Oryx beisa.